Common-battery automatic telephone system.



w. L. CAMPBELL.

COMMON BATTERY AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JULY 9, |907.

W. L. CAMPBELL.

COMMON BATTERY AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JULY 9, 1907.

vPatented. Apr. 27, 1915.

SHEET 2.

-. 3 SHEETS 'foga/@QW W. L. CAMPBELL.,

COMMON BATTERY AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED IULY'Q, I907.

l., 137,200. Patented Apr. 27, 1915 3 SHEETS--SHEET 3.

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initiieren sTATns PATENT creeren wILsoN L. c'AMriBELL, oF LA GRANGE, ILLINOIS, AssIGNoR, BY MEsNE ASSIGNMENTS, To FIRST TRUST AND SAVINGS BANK, TRUSTEE,- oF CHICAGO, ILLINOISa COMMON-BATTERY AUTOMATIC TELEPHONE SYSTEM.

Specication of Letters Patent.

'ra-tenten Api, 27, iota Application filed July 9, 1907. Serial No. 382,900.

To all '107mm t may concern:

Be it known that I, WILSON L. CAMPBELL, a citizen of the United States of America, and resident of La Grange, Cook county,

Illinois, have invented a certain new and ing current to the calling subscribers line,

but no current is supplied through the connector to the called line lfor talking purposes. in other words, certain windings of I+che calledHsLbscribers individual trunking switch constitute the sole medium for feeding talking current to the called subscribers line,`so that the called subscribers line receives talking current through the medium of thcnormal connection therefrom to the common battery. The calling 'subscribers line, as stated, then receives talking current through the windings of the connector, as

'will hereinaftermore fully appear.

In the accompanying drawings Figure 1 shows diagrammatically a calling substation A and a called substation A.' `connected through the medium `ot automatic' switches C, I) and E. To the line No. 500 of substation A there is allotted thefswitch C, of an improved type, known as a line switch; and to the line No. 220 .of the substation A there is allotted a similar line switchA C',l

At I) is represented a iirst-selector switch, and at E is shown a4 connector-switch in connection ,with y.which I have elected Ato explain my invention; the former being of the general type described in Patent No. 8l5 ,`$21, granted March 13, 1906, to Keith, Erickson & Erickson, and the latter being l an improved form of the connector shown.

TVD"tent No. 815,176, also granted March W5, to Keith, Erickson & Erickson. Yster switch F'is provided for congroup of line switches of which C member..y For operating4 and talkingl purposes a central battery B having its positlve terminal 'preferably grounded at G is used. '1

-I `ig. 2 is an enlarged diagram of the line switch C and its master Swltch F. Fig. 3 is a detail View of the master switch bank. Figs. 4:., 5, 6, 7, 8, 9 and '10 are detail views showing the construction and operation of the impulse Vsprings of the subscribers telephone.

It will be understood that the tiret-selec tors and connectors may be employed upon a percentage basis-that is, in an automatic exchange of one-thousand capacity, a .somewhat common arrangement is to divide the subscribers and their allotted line switches into groups of one-hundred each. Then to each group'of line `switches there is allotted l aV group of .51st-selectors, usually ten in number, making 1n a one-thousand system one-hundred first-selectors. Then to cach bank level of these Hist-selectors there is 'allotted a group of connector-switches, usually ten in number, which in turn are adapted to make connection with the subscribers lines of that group. For example, the group corresponding to the first level is the onehundred group; the group of the second level is the two-hundred group, etc.; this to each hundred group of subscribers of the thousand there is allotted a group of connector switches, so that in a one-thousand system there would'be one-hundred connectors, when arranged on a ten per cent. basis.

The substations may be of any suitable or approved type. "Those in, connection with which I have elected .to explain my invention comprise, as shown atv station A, a re- 'ceiver 2, a switch-hook 3 for controlling the substation circuits, which controlling operations are accomplished through the medium' of any suitable means, such as the. cam-arms 4, 5 and 6. As the switch-hook is lowered the cam-arm 5 momentarily presses the rei lease springs 7, Snand 9 into engagement,

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whereby the substation line conductors may Abe grounded simultaneously. 'l/Vhen the switch-hook is down the cam-arm 6 maintains a contact between the springs l0 and 11, thereby bridging the ringer 12 in series with the condenser ,13V across the line.

vThe substation ground circuit is` normally broken between the lground springs 14 and `15 byv the. cam-arm 4, but when said 1.19

springs are-together ground potential is then provided to the ground post 16, and to the .Y release spring 7, as 1s usually the case in telephones of this type. The said substation comprises the usual transmitter 17, induction-coil -18' having the primary winding 19 and secondary winding 20. Being an auto- -matic substation it is provided with the usual vertical and rotary impulse springs 21 and 22. The vertical impulse spring is provided with an oblique projection or lug 23 on its'under side (Fig. 4) with which the vertical impulse teeth 24 are adapted to engage for driving the spring 21 intermittently ontothe ground post 16. The lrotary impulse spring 22 is provided with a somewhat similar mechanism, by means of which the rotary impulse spring i driven onto the ground postonce when the dial is rotated in one direction, and once when rotated in the opposite direction, The said rotary impulse spring 22 has on its under side a J-shaped Ymember 25 having two sides c and d, and there is, in addition, an auxiliary spring 25 which works in conjunction with the V- shaped member. As shown more clearly in Fig. 4 the auxiliary spring 26 is provided with a lower curved part 27 having'the rear section e curving outwardly, as shown in Figs. 4, 5 and 6. The front section 2S oi' the said member 27 is designed to iall just below the apex of the V-shaped member 25, so that the rotary impulse tooth 29, when moved in the .direction indicatedby the ar row in Fig. 5, will 'pass onto the curved member 27, thus pressing the rotary impulse spring 22 onto the ground post 16'or a comparatively long time, as shown in Fig. 6, and sending a compi ratively long impulse to the line. As the impulse wheel advances-,.the vertical impulse teeth 24 approach the lug 23 of the vertical impulse spring 21 (Fig. 6), and eventually the first tooth that meets the lug 23 clears or disengages the said lug, as shown in Fig. 7, but not until after the rotary impulse tooth 29 clears the curved member 27. As the impulse Wheel continues to advance in the direction indicated by the arrow in Fig. 7, the succeeding impulse tooth will clear the projection 23, as shown in Fig. 8. Then, when the impulse wheelris released, first the vertical impulse spring 21 is carried into engagement with the ground post 16 twice by the teeth previously cleared or disengaged, as indicated in Fig 9; but as the impulse wheel 'nears its normal position the rotary impulse tooth 29 passes under the curved member-27 of the auxiliary spring 26. (Fig. 10), engaging the V-shaped member 25 directly and for a'short time only, sending the ordinary impulse through the medium of the rotary impulse spring 22 to the line, after which the said member 27 is cleared, as shown'in Fig. 5, as the impulse wheel reaches its normal position. its thus `with the locking dog 31'.

`by the pin 50 to described, the operations are repeated each time that" the dial is turned, and 'the number of impulses produced through the medium of the vertical impulse spring are accurately and definitely vdetermined at each operation of the dial. Said substation is, of course, provided with a dial which is not Shown, but which is secured to the shaft 30, together Furthermore, there is a lockingcam 32that locks the dog 31 while the receiver is on the switch-hook, to revent a rotation of the dial.

y ld or operating the impulse springs 21 and 22 the substation is provided with an impulse wheel 38 that is secured to the shaft 30, which impulse Wheel carries on its periph ery the so-called vertical impulse teeth 24 and one rotary impulse wheel' 29. The said impulse teeth are so arranged that when the dial is drawn down the rotary impulse spring 22 is pressed into contact with the ground post, and the impulse spring 21 is not carried into contact with the ground post 16; but as the dial returns, first the vertical teeth engage the vertical impulse spring 21, and after they have completed their work the rotary impulse tooth 29 operates'the rotary impulse spring 22. In this operation the subscribers rotary line conductor 35 is. given a so-called preliminary impulse, thenthe vertical line conductorv 34 is given'a number of ground impulses, and then the rotary line conductor 3'5 'is given another ground impulse. It will be seen that as long as the dial isout of normal position the dog 31 springs 36 and 3 to separate, thus preventing the impulses that are delivered to either .line conductor from passing to the other.

Means whereby asubscriber 'may signal a. called subscriber comprises the pushbutton 38 which,` when pressed, carries the spring 39 out of engagement with thefcontact point 40 and into engagement, with the contact point 41, whereby the vertical line conductor 34 is grounded.

The line switch C (Fig. 2) comprises a plunger 42, plunger-arm 43, trip magnet 44 and switch-release magnet 45, all of which are built about a suitable base or frame not shown. The said switch-release magnet is provided with an armature 46 that is pivoted on a pin 47 which rises from the base of the switch. The said armature carries pivotaly secured on its end a second armature 4f that 1s controlled by the trip magnet 44. The pin 49 about which the armature 48 moves is carried on the end of the armature 4G. The plunger 42 is pivotally secured the plunger-arm 43, whic latter is in turn pivoted -to aA pin 51 that rises from the switch frame (not shown). The lug 52 is stamped out of the side of the frame and is provided as a stop Jor rest for the armature 46. Upon the armature 48 is loo ermite the primary circuit @cured the catch spring 53 which is adapted tocngage the' end 54 of the plunger-arm 43. Furthermore, upon the end yof the plunger-arm 43 there is the arm 55 having on its end the insulating bushing 56. This arm is so arranged that when the plungerarmoperates and thruststhe plunger into the bank, the springs 57 and 58 are carried out of engagement. with the springs 59 and 60, respectively, whereby the trip magnet coils are disconnected ,from the battery, terminals. The trip magnet 44 comprises two double-wound coils 61 and 62, having the windings differentially arranged, so that .when one set of windings of the two coils carries current the trip magnet 44 pera- .tively energizes; but when both sets of windings are included in series in an energizing circuit the said magnet does not operatively energize. y i f The general operation of the switch is as follows: The trip magnet 44 is energized by a preliminary impulse sent over the rotary eide 'of the .line by the forward rotation of the dial, and the armature 48 is lattractd*against the magnet cores. When the armature 48 is attracted to the left (Fig.

v 2'), the catch 53 slides out of contact with fill the end 54 of the plunger-arm 43, and the said plunger-arm 43, owing to the tension of' the spring '63, moves about the pin 51 and thrusts the plunger 42 into the bank terminal Q. When the plungerar1n 43 thus operates, the arm 55 operates the springs 57 and 58 to disconnect'the trip magnet from thebattery, as explained; and when the trip magnet. denergizes, the trip armature 48 falls against the end of the plunger-arm 43. The switch is restored when the release mag-A net 45 becomes energized, whereby the armature 46 is attracted and, accordingly, the trip armature 48 is moved upwardly until the catch 53 slides over the end 54; then when `the releasemagnet45 becomes deenergized'the armature 46 returns to normal` position and remains at rest against the-stop Furthermore, since the plunger-arm 43 isV new in engagement withA the armature 48, the-said pluimger-arfil'` 1s also moved 'about the pin 5 1', whereby the plunger 42 is removed from the bank terminal yQ. Als'c, since vthe plunger shaft has advanced one step, the hub 64 of the plunger 42 comes to .rest in the position shown by the dotted lines in- Fig. 2,' againstthe plunger shaft'65; and as. the said plunger shaft advances each time an idle trunk is seized, `the' plunger 42 is not advanced,but remains in this position opposite the 'trunk terminal from which it hasl )ust disengaged, since the slot 66 1s not in engagement with the plunger shaft 65. After allo'f the trunk lines havebeen successively seized,v and the plunger shaft again passes tothe .position it occupied when v the plpnger-48'seized therterminal' Q, the

plunger 42 now returns to normal locking engagement with the said-plunger shaft. In the meantime, if the line switch C is again operated, the plunger 42 again engages the same terminal, the terminals usually being ten in number, but only one of which is shown at Q. The said terminal is shown turned from. its true position with respect to the swing of the plunger 42, and the bushing 67 is correspondingly turned, all for the purpose of making the illustration clearer. The terminal Q comprises the springs 68 and 69, 70 and 7l, 72 and 73, and 74 and VThe said springs are normally disconnected from each other, but are driven into contact in the above-mentioned order when the plunger 42 engages the terminal Q.' Normally the plunger 42 is, however, retained out of engagement. with the line switch bank, and in either locking or sliding engagement with the plunger-controlling shaft 65, which latter is operated by the master switch F. By sliding engagement I mean that the slot 66 of the plunger 42 does notfengage the plunger shaft 65, and as the plunver shaft is turned the hub 64 slides upon tlie shaft; but when in locked normal position the slot 66 is in engagement with the shaft 65, and each time that the shaft is advanced the plunger `42 is also advanced.

The master switch F, which may be of any suitable or approved type, is provided for operating the plunger shaft 65, and for controlling certain circuits that will be disclosed hereinafter. It comprises lthe fol lowing details: A motor magnet 76 for oper# ating the ratchet wheel 77, which latter is designed for operating the plunger shaft through the medium of the cam 78; also a differential relay 79 for controlling the energizing circuit of the motor magnet 76. The

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said master switch also has a bank O comprising a plurality of indiyiglual contact segments a andA a common metallic segment 80, as shown in Fig. 3. The wiper 81 is adapted to remain in constant engagement with the bank 0,'and to maintain at alltimes, except whenthe 'wiper is passing from the Iextreme left contact 82 to the extreme right Contact 83, some one of the segments a in electrical connection with the common segment 80. As shown in Fig. 3, the individual segments a are separated from the common segment bythe insulating strips 84. The spring 85 is providedfso that when the wiper 81 passes to the last-,contact point 82, then on the next step the wiper is carried to the contact 88 on the extremo right and the upper part of the wiper 81 slides on the guide Spring 85, thus preventing the wiper from placing any of the individual segments a in contact with .the commonsegmentSO, whereby some interference might be caused with fthe. master vzo `by-step'inanner by the ratchet wheel 77, through the medium of the cam member 78 rigidly secured to the 'sa-'id wiper 81 and adapted to successively engage the pins 86, 37, 88 and 89 upon the said ratchet wheel 7 7 The motor magnet 76 is providedl with an varmature 90 upon the end of which there is suitably secured a pawl 91. -Each time that 'the said magnet is energized the pawl 91 engages the ratchet ,wheel 77, advancing the latter one step. 1t will be seen, therefore, that as the ratchet wheel 77 advances, the wiper 81 also advances step-by-step from right to left, and when the pin 86,. for instance, clears the cam 78 the retracting spring 92 restores the wiper 81 to its .irst Yposition at the right of the bank in engagement with the first segment 83. The said' motor-magnet 76 1s provided with a couple of interrupter springs 93 and 94fthat are 1ncluded in the energlzing circuit of the said motor magnet, which energizing circuit also comprisesthe springs 95 andr96 controlled by the diderential relay 79. Therefore, .whenever the diierential' relay is energized the springs 95 and 96 are pressed into'contact, and the motor magnet 76 operates ste by-step as long as the differential relay 9 remains energized. Furthermore,v it 1s assumed thatthe 'terminal Q of the line switch C is the first terminal of the line switch bank.. The plunger 42, while in normallocking engagement with the shaft 65, is retained in front of said terminal by the plunger shaft 65 whenever the master switch wiper 81 is in engagement with the bank seg-l ment 83; but as the motor magnet 76- advances thewiper 81 onto the second seg ment 97, the said plunger and all idle plungers similarly engaging the shaft 65 are carried opposite the next terminal of the line switch bank It should be noted Vthat in each switch 'bank all of the springs 68 are per-v -man'ently connected and maybe made of one common piece. The springs 69= hiwever. are individuaL-that is, there is one separateand distinct spring for every bank set Q, there being ten in thev bank. The springs 70,72,

73 and 74,:like the spring 68, are also common,'and the springs 71 and 75, like the springs 69, are individual. For every bank terminal Q there is a trunk line of three conductors 98, 99 and 100 leading to a selector, and there is also a normal' trunk line comprising the conductors 101, 102 and'103` leading to the connector banks. The subscribers line conductors 34 and 35 terminate in the springs 68 and 70 which, as hasbeen stated, are common springs. When the subscriber operates the line switch C and the plunger 42 engages the terminal Q, the sub scribers line conductors 34 and 35 are extended to the vertical and rotary trunk coni d ctors 98 and 99, and thence to the switch D.

les.

Llhe mechanical details of the first-selector switch 's 'aft (not shown) -w tary -lme i position,

-th e same. `sv'vitchshaft (not shown), like the selector,

' private wiper are in enerai' well `known involving the iiich carries the line wipers 104 and 105 vand the rivate wiper 106.' The side switch iscontro led by the private magnetl`107, and when the side switch is in normal or' first psition the side switch wipers 108, 109,110 and 111 engage the contact oints 112, 113, 114 and 115, respectively. n the second position the side switch wipers engage the`contact points 116, 117 '118 and 119, and whenthe wipers are in third position the contact points 120, 121, 122 and 123 are engaged by their respective wipers. After' the line switch C has operated and a trunk leading to a first-selector has been seized, the rstselector is then under the control of the lcalling subscriber, throu h the medium 4e the vertical and rorelays 124 and 125s While the side swith is in first position the calling subscriber controls the vertical magnet 126 which operates to give the switch shaft avertical motion.

v Bymeans oi the rotary line relay 125, and

whi e' the side switch is in first or second the subscriber controls the private magnet 107 and, thercfore,the sideswitch.

When the side. switch is in second position the rotary magnet 128 is energized., and the lswitch shaft that carries the wipers 104, 105

and 106 is operated in a rotary. direction. The vertical and rotary line relays 124 and 125, acting conjointly, provide the means by which the release magnet 129 is operated by.-

the subscriber while the side switch 1s in first o1' second position. If the side switch passes to third position, however, (since the selector D is of the trunk-release type) the release magnet 129 is' then controlled through the connector E by way of the prireleaserelay 130.

The mechanical details of the selector and connector, asis well known', ,are very much For instance, the connector carries the tline wipers 131 and 132 and the v133. The connector switch is also bcontrolled 'by the ctlling subscriber throu h lthe 4medium'of the vertical and rotary lline relays 134 and. 135. The vertical line relay 134 directly controls the vertical magnet 136--and also the rotary magnet 137. The purpose of the vertical magnet 136 is to give the shaft and shaftwipers a vertical motion, and the rotary magnet 137 imparts tothe shaft and shaft Wipers a rotary or cir- .vate wiper'106 and by means of the backcular motion. The rotary line relay 135 coni trols the private magnet 138, which latter, under certain conditions, vcontrols in turn the vertical and rotary magnets 136 and 137,

the release magnet 139! and also the side switch wipers 140, I141, 142, 143 andi144. Preferably, the said side switch, like the side switch of the selectorfhasa normal or 'first .Y

position, a second positionanda third pcf sition. The release magnet 19 1s also controlled by the vertical and rotary line relays 'third position an energizing circuit is closed through the said relay. By means of the differential relay 147the energizing circuit.

through the ringer relay is controlled', and when. the said relay 150 denergizes, while the side switch is in third osition, the ringer" generator H is bridged across the terminals of the called line to signal the called subscriber. From the foregoing it is evident that the operation of the ringer relay, as arranged in the connector switch- E, is just the opposite of the operation of the ringer relay as disclosed in the said onor patent-that is, to bridge the ringer water across the called line the ringer` rey must be denergized, instead/of eneras is usually the custom. The central tion is equipped with the busy-signaling apparatus i of any suitable design, as, for ample, the one comprising an interrupter 1 in series with the primary winding 152 ol: the induction-coil 153,' whereby a busysignaling current is induced in the secondary winding 154 ot' the said induction-coil 153. The secondary windingy 154 is 'connected with the side switch wiper-144,and when the .normal springs 155 and 156 are in contact,

and the side switch is in first position, the busy-signaling current may be'transmitted to the calling subscriber.

The operation of my improved line switch C may be more clearly understood from a description of its action whenone subscriber calls another, as follows: To c 'all substation A (No. 220) the Subscriber 'at substation A removes his receiver from the switch-hook and operates the calli-ng device or dial once, in the well-known manner, for each digitthat is, when the dial is rotated for the first digit a preliminary `impulse is transmitted over the rotary line conductor. This preliminary impulse energizes the trip magnet 44, whereby the line switch C is operated to seize an idle trunk line leading to a firstselector. The dial, in returning to'normal position for the first digit, operates the firstselector switch to establish connection with an idle trunk line leading to a connector. It will be understood, of course, that whn the dial is turned for each digit a preliminary rotary impulse' is transmitted to the rotary line by the forward rotation of the which impulse, if the selector E or nector E is on thelinegis receiv tary line relay of the switch w switch is in first position. ,This re relay energizes, of course, but withon since the side switch is in po the switch is not operated until the cia livers the vertical impulses by rotation. Said preliminary impulse is' e ctive only in operating the line switches. The impulses for the last two digits are directed toward the connectorE, which operates 'to place its shaft wipers in connection with the contacts corresponding to the called line. t The preliminary impulse foroperatingthe line switch C, that occurs when the calling` subscriber rotates the dial forward for the first digit, is caused by .the rotary impulse spring 22 being pressed against the ground a post 16. As a result of the impulse the trip magnet 44 of the line switch C is energized by alow of eurreiit from ground G to the springs 14 and 15, ground post i6, impulse spring 22 to the rotary line conductor conductor 159 (F ig. 2), throdgh the f ings 160 and 161 of the trip re tery lead 162", thence through bat ground G. As soon as the trip energizes, the armature 48 is attraV c and the plunger 42 is liberated and thrust into the bank terminal Q (assuming-r that the plunger 42 is opposite this particular terminal at the time) by the spring 63.' The loe plunger, upon thus operating, moves the plunger-arm 43 about the point 51, whereby the arm 55 on the end of the plunger-arm carries the springs 57 and 58 out of en;l ment with the springs 59 and 60. The gagement of the springs 57 and 59 breaks energizing circuit through the trip magnet 44; the said trip magnet then denergizes and permits its armature 48 to fall bael'm that is, the spring catch 53 falls f terminal piece 54, as shown, 'hen vthe plunger 42 engages the bank terminal an energizing circula is closed through the motor magnet relay 7 9, which in turn operates to. close an energizing circuit through the motor magnet( 76. The motor magnetthen operates to advance all idle plungers that are in locking engagement with the 'shaft 65 to a point opposite the next idle banlr terminal, similar to the terminal Q. The through the relay 79 extends from ground g2 through the winding 163 ofthe relay 7 9, segment 80, wiper arm 81, segment 83, conduetor 164, bank terminal springs and 7 4, release magnet 45 to the. battery leadil, thence through battery B to ground A"- though this circuit includes the release magnet 45, the magnet iii-does not operatively energize, since the windings of the relay are of a' high resistance, while the winding iso of the release magnet is comparatively low. The relay 79 upon energizing operates to place the springs 95 and 96 in contact, whereby acircuit is completed through the motor magnet 7 6, extending from ground G3 the springs 95 and 96, motor inag- 93 and 94, through the motor magnet 76 t0 the battery lead 162, thence through battery B to ground G. The motor magnet 7 6, upon energizing, attracts its armature 90, whereby `the pawl 91 engages the ratchet wheel 77 and rotates the wheel one step. When the armature 90 is attracted against the magnet cores the springs 98 and 94 disengag'e, ing circuit through the motor magnet. rlhe cam 7 8, being inengagement with the pin 86, is'operated to advance the plunger shaft 65, and consequently all idle plunger-s that may be in normal locked position with the shaft 65, one step and to a point opposite' another net springs trunk terminal, similar to the terminal Q (assuming the next succeeding trunk to be idle). Consequently the wiper 81 is carried from the contactl point 83, which 'correspends to the terminal Q, to the contact point 97, which latter corresponds to the terminal before which the advanced idle plungers are now resting.

. Suppose that nine subscribers have called and that the masterswitch has been thus ,operated nine steps, carrying'the wiper 81 to the last Contact ,point 82. Now, when the motor magnet 76 operates for the next step, and when the tenth subscriber calls, the wiper 81 passes back and drops into engagement with the contact point 83, as already explained. If the first. trunk is still busy the wiper 81 inds battery current on the contact 83, and an energizing circuit is established. through the dierential relay 79, which in turn opera-tes to close an energizing circuit through the motor magnet 7G. The current through the said relay 79 flows from the said contact 83 through the wiper 81 to the common segment 80, through the winding 163 of the diii'erential relay 7 9 to o'round G2. `When the ditlerential relay 9 attracts its armature the diii'erential relay springsl 95 and 96 are pressed into contact, thereby closing an energizing circuit forthe motor magnet 7G from ground GB through the said springs 95 and 96, through the motor magnet springs 93 and 94, mo tor magnet 7 6, thence to the battery lead 162, and through battery B to ground G. The motor magnet then operates, as previously explained, -to' rotate lthe ratchet Wheel 77 one step for advancing the plunger shaft `(i5 one step, and the master switch bank wiper '81 one step also, and into en gagement with the second segment 97. The

plunger shaft v when thus advanced one' ste carries all idle -plungers that arein loc ed engagement with the. said shaft to thereby breaking the energia-- menace a point opposite the next bank terminal, as

previously explained. Y It there should still 7 (i is again operated, whereby the 'plunger shaft 65 and the master switch wiper 81 are advanced another step. This operation continues as long as the wiper 81 continues to find segmentsv with guardingpotential. As

soon as an idle segment is found, however,

the energizing circuit through the differential relay 7 9 is-broken, at which time the said relay in turn breaks the energizing circuit for the motor magnet 76 until Athe next subscriber makes a call. At the'inetant that the plunger 42 enters the said bank terminal Q the following springs are pressed into contactz'68 and 69, 70 and 71, 72 and 78, and 74 and 75.

The engagement of the springs 72 and73 establishes a guarding potential by way of the normal conductor 103 to the connector 'private bankcontacts corresponding to 4the line that terminates in the lineswitch C, to prevent any subscriber from calling the4 said line after the calling subscriber at substation A operates his dial preparatory to making a call,'as explained. The-circuit over which the said guarding potential lis established extends from ground G4 through the bank springs72 and 73 to the. private' normal conductor 108. Also, the closure of' connection between the springs 74 and 75 establishes a guarding potential at the master switch bank contact 83, over the ollows ing circuit: From battery B to the battery lead 162, thence through the release inagnet 45 and springs 74 Aand 75 over the conductor 164 to the said Contact point 83. 'It will be understood that the bank terminal Q, being the first bank'terminal of the line switch bank, corresponds to the first segment 88 oi' the master switch bank G and, therefore. to the trunk line conductors 98,

99 and 100 which 'terminate in the selector D. This guarding vpotential protects the lseized. trunk conductors 98, 99 and 100 Vtrom being seized-by other plungers, as already explained. The closure of connection4 between the springs G8 and 69 extends the calll ing subscribers vertical line conductor 34 to the vertical trunk conductor 98, and to the side switch wiper 108 of the first-selector D.. The closure of connection between the springs 70 and 71 in a similar manner extends the subseribers rotary line conductor 35 to the rotary trunk conductor 99 and to the side switch wiper 109 ot the selector D. The subscriber has thus established connectionlwith the selector D, which latter is menace now operated by the impulses that are delivered as the dial returns' to normal position. The first digit being 2 the spring 21 is pressed onto the ground post 16, twice.

As a result the vertical line .relay 124 or" thev trunk conductor 98, side switch wiper 108 of the selector D, contact point 112, vertical line relay 124 to the battery lead 162, thence through battery B to ground Gr. Each time -that the vertical 'line relay 124 energizes, the line relay. spring 166 is pressed onto the ground spring 165. The vertical magnet 126 is thereby energized, and the wipers 104, 105 and 106 of the selector D are raised to the second bank level and brought opposite the first Contact of the level. The energizing circuit for the said vertical magnet 126 extends from .ground G5 through the springs 165 and 166, private springs 167 and 16S-to the vertical magnet 126, thence to the battery lead. 162, and through battery B to ground G.

Following the vertical impulse the rotary impulse spring 22 is pressed onto the ground post 16, grounding the rotary line conductor 35 and energizing, therefore, the rotary line relay 125 of the selector D. The energizing current passes from ground G to the rotary line conductor 35, thence it Hows through the line switch bank springs Z0 and 71, rotary trunk conductor. 99, side switch wiper 109 of the selector D, 'Contact point 113 to the rotary .line relay 125, thence to the battcry lead 162, and through battery B to ground G. The rotary line relay upon energizing presses the line relay spring 169 onto the ground spring 165, thereby establishing a circuit through the private magnet 107 from ground G5 through the springs 165 and 169 to the private magnet 107, and through the said magnet to the battery lead 162,

thence through battery B to ground G. The private magnet, upon energizing and deenergiaing, permits the selector side switch to pass from first to second position, permitting the side'switch wipers 110 and 111 to engage thecontact point-S118 and 119, re- Spectively. The closure of ,connection between the vside switch wiper and the contact point 118 sets up an energizing circuit for the rotary magnet 128 from ground G to to-the contact point 118, through the side switch wiper 110, interrupter springs 170,1'0 tary magnet 128 to the battery lead 162, thence through battery B to ground G. The said rotary magnet 128 then operates to ro tate the wipers 104, 105 and 106 of the selector D into engagement with the first contact ofthe second level of the selectorD,

from which contact it is assumed the line conductors/'171, 172 and 173 lead to the connector E. 1f the first trunk is busy, however, and the wipers have to pass over busy trunk lines, then as soon as the private wiper '106 engages the first. grounded private'bank contact point, the private magnet 107 ener gizes again,locking the side switch in second position. v The energizing circuit for said private. magnet extends from the grounded terminal G of battery B through an occupying switch (not shown) to the private -'wiper 106, thence over the conductor 174 and through the back-releaserelay 130 to the side switch wiper 111, contact point 119, private magnet 107, thence through said magnet to the battery lead 162, and through battery B to ground G. .The private magnet 107upon thus becoming energized, locks the side switch wiper 1.10 in engagement with the contact point 118, whereby the rotary magnet 128 willbe energized,step-by-step until the wipers are carried beyond the last busy trunk line. At the instant that-the private wiper leaves the inst busy contact point the energizing circuit through the private mag net 107 is destroyed, and as a result the selector side switch passes to third position. It, however, there are :no busy trunk lines the private magnet 107' releases the side switch to third position as soon as the wipers are carried into engagementfwith the first trunk iine. Assoon as the side switch passes third position, as stated,the subscribers line conductors 3-1 and 35 `are extended to the ,l i

conductors 171 and 172, which in this case, it is assumed, lead to the connector switch The extension of the line occurs, of course, as soon as the side switch'wipers 108 and engage the. contact "points 120 'and 12.1, re-

spectively. Not only is the 'subscribers line thus extended, but i guarding potential is established at the private wiper 106 when the side switch wiper 111 passes onto the ground contact point 123, :for protecting the seized if.

trunk line from interference by'other caiiing subscribers. established from ground G7 to the conter point 123, thence through the side swi wiper 111 and through the back-release his guarding potentiai is lay 130, conductor 175iv to the'private wipe?- 106.' v it will be seen, of course, that the cnergizingvcircuit for the rotary magnet 128, which reference has alreadybeen made, is destroyed when the idle trunk line is seized-that is, when the side switch wiper 1101eave's the contact point 118. The groundL ing of the line conductors 34 and 35 for the lasttwo digits affects the connector byoper ating the vertical and rotary line relays134. and 135. `When the said vertical line conductor Biis grounded the vertical line relay 134 is energized by a. iiow of current from the substation ground GY', vertical impulse spring 21 to the vertical line conductor 34, 1315 -tial relay 147 to the battery lead 162, thence through battery B to ground G. The winding l148 of the relay 147 being included inl this circuit, the said relay energizes, but its operation at this particular time is. without eil ect. Each time that the vertical line relay 134 operates for thesecond digit, the vertical magnet 136 operatively. energizes to carry the shaft wipers 131, 132 and 133 in a ver-I tical direction, one step at a time, until thesaid wipers are carried up 'two steps and thus brought-,opposite a level in which are subscriber operates the dial as -l so located the terminalsl of the line #220.

The circuit through thevertical4 magnet 13G extends from ground Gil*v through the -springs 176 and 177, private magnet springs 178 and 179, vertical magnet 136,`side switch wiper 142 -to'the battery lead 162, thence through battery B .to ground Gr.4 When the rotary line conductor 35 is grounded, following the grounding of the vertical line conductor, the connector rotary line relay 135 becomes energized through a circuit extending from the substation ground Gr'y `\through the rotary impulse spring 22, ro

tary hneconductor 35, anlg springsv and 71, conductor 99,- siue swltch wiper 109, shaft wiper 105, conductor 172, rotary line relay 135, vwinding 149 of the differential v relay 147, through the springs 180 and 181 tothe battery lead 162, thence through bat-v tery B-to ground G. The Windin 149 of the differential relay 147 being yinc uded in this circuit, as is the winding 148 in the vertical line relay circuit, the said relay energizes, but with no' effect. ,The rotary line relay 135 upon energizing operates to close an energizing circu`1t` 'through the private magnet l38,.which latter in turn operates to release the side switch from lirst' to second position. The energizing .circuit through the private magnet 138 extends from ground G8 through the springs 176 and 182, through the private magnet 138, springs 180 and 181 to the battery lead 162, and through battery B to ground G.- For the last digit the lpreviously described, grounding the vertica linel conductor 34 ten times andthe `rotary line conductor 35 once. IThe connector vertical and rotary line relays 134 and 135 are operated over previously traced circuits. However, whenthe vertical line relay operates, a circuit is closed through the rotary magnet 137 instead of, through the vertical magnet 136, since the side switch' wiper 142 is now in second position. Each ltime that the rotary magnet is energized the shaft wipers 131, 132 and 133 are rotated one step at a time untilV the said Wipers are carried into engagement with the normal conductors 183 184 and 18.5, the first two of which con ductors lead to the line terminals of the desired substation. Thel vrotary line relay '135 upon energizing completes anlenergizing circuit through the private magnet138, as before, which latter now operates with one of two rcsults, namely the release of the 4side switch from second to third position,

or the so-called busy-release of the connector. It will be assumed that the former 1result occurs and thatthe side vswitch passes to thirdposition, whereby the side switch wipers 140 and 141 are placedl in connection with the shaft wipers 131 and 132, respectively. Furthermore, when the side switch asses tev third position a guarding potential '132 are disconnected from the ringer generator terminals and connected with the callling subscribers extended conductors, and the calling substation is provided with battery current for talking purposes. The cir- 9 cuit through the ringer relay 150 extends o from ground G", side switch wiper' 143, con* ductor 18" ,hrough the winding of the ringer relay 150, differential relay springs 188 and-189, contact point 187,'side switch wiper 142, 'battery lead 162, thence through,

'battery B to .ground G. The ringer relay upon energizing operates to shift the springs 1902 191 and 180 out ofeng-agement with the springs 192, 193 and 181 and into engagement with the springs 194, 195 and 196, re-

spectiVely. WVhen the spring 180 is shifted from the spring 181 into engagement with the spr1ng196 the conductor 197 is changed from the negativevpole of the battery B to the grounded positive pole. In order to signal the called subscriber the calling subscriber presses the signaling button '38, whereby the `vertical line conductor-34 is grounded and the connector vertical line .relay 134 and .the differential relay 147 become energized as before. At this particular time, when the relay..147 operates to separate the springs 188 and 189, the energizing circuit 'through'the ringer relay is broken. The said relay denergizes and permits the springs 190,191 and 180 to resume their normal position, whereby the 'ringer generator terminals are bridged across the yline terminals of the called' substation. l' f A signaling current is sent from the generator H to the ringer relay springs 193 and 191, si'de switchwiper 140 shaft wiperA 131, vertical normal conductor 183, vertical 212, windings LJ sommi ndcmf duco $98, svlMgs t0n springs, aizs ing 2li@ in the yc/E rot@ m'ua com; windings mii i0 tha m/ @hence woug erj; B t@ gzounf "UH Tha wnngs of he switch 'p 1mg et a te so aux paged dm wen tha windings f and thus caly currnt in Seas 'with he vindngs 215 and m6, the Sa maglie-, does 310% Opernvdy energize. The above aimait through tha Spring rp magme 20S gnoves the cnled subst circuitft "csic slf'mf pur winding per i to znfd position. El

curz'm passes QX- Swieh m Y @remt over which dus enin relay lease magnet 139, conductor 197, springs 180 and 131 to the battery lead 162, and through lbatlfery B to ground G. Nhen the connector release magnet 139 .is thus supplied with current it onergizc's, and as a result the switch. shaft and side switch are restored to normal position, thus breaking the connection between the connector switch shaft wipers 131, 132 and 133 and the normal con ductors 133, 184 and 185. The baCk-releaSe relay 130, being in the lsame circuit with the release magnet, energizes simultaneously with the latter and operates to close a circuit through the selector release magnet 129 by pressingtogethcr the back-release springs .222 and 223, Also, when the springs 222 and 223 engage an energizing circuit is closed through. the release ma net 15 of the line switch (l extending lrom ground through the springs 222 and 223, bank springs 75 and 7a, release magnet 1-5 to the battery lead 162, thence through battery B to ground G. The circuit through the said release magnet 129 extends from ground through the release springs 222 and 223, through the release magnet 129, thence to the battery lead 162, and through battery Bto ground G. When the ground tothe line conductors 34 and 35 is interrupted all the magnets involved in the release aredeenergized and all the switches are fully restored. 1f the called line #220 is busy at the time that the calling subscriber #500 attempts to 'establish connection, the connector E is released by the last impulse to thc rotary line conductor 35, as follows: The

said impulse energizes the rotary line lrelay 135 of the comiector E, which relay in turn energizes the private magnet 138, pressing the private sprin s 224: and 225 into contact after the private wiper 133 has been nector s carried onto the grounded private bankv Contact, lt course, itis understood that whenever the line :#:220 is busy the conhectory private bank contacts connected with the private normal 185 are all connected to lground'. Therefore, sinceithe connector side' switch 1s in second position when the rivate magnet springs 224- anol 225 are broug t into contact, an energizing circuit is established through the release magnet 139 from the said grounded private bank contact to the private wiper 133, thence to the side switch wipery 1113 (which is in second position) to the private magnet springs 224 and 225, to the release magnet 139, through the springs and 131 to the battery lead 162-, thence tl'irough battery B to groundG. The convitch shaft and side switch are thus released andy connection is not established with the called line. Now, when the calling subscriber presses the signaling button, the vertical line relay 134 lbecomes energized and operates to close a circuit through the vertical magnet 136. The vertical magnet Awindings 213, 211, 215 and 216 of tlie trip magnet are the only resistance windings by which the battery is normally bridged across the called subscribers line. In othervwords, the called subscribers line receives talking current through the medium of its normal connection with the opposite poles of the common. battery, and through no other me-I dium. The calling subscribcrs line, however, receives talking current through the medium of the windings of the line and differential relays in the connector, and these y line relays are energized during conversation. The Adifferential relay, however, remains de'e'nergized until the calling subscriber hangs uphis receiver, at which time the differential windings are unbalanced. and a release'is effected. lt will also be seen lthat during conversation the trip magnet which is individual'to the called subscribers line is not energized, as its windings oppose each other when connecte(` .in series.

It will be understood, of course, that the windings of the trip magnets have suihcient impedance to, prevent the passage of voicecurrents therethrough. When one subscriber callsanother the trip magnet of the calling 1 line has its bridge cut otl' or opened up, but

the trip magnet of the called line remains connected therewith to serve as a means for feeding talking current thereto. It will be seen that the called subscribers trip magnet does not energize when he hangs up his receiver, for the reason that at such time `there is no ground connection wi th theA line at the substation. In other words, the called subscriber has not operated his dial, and consequently the ground connection which is used for releasing purposes is not closed, and the downward movement of the switch-hookdoes not ground the line. 0f

course, when the subscriber calls, he then puts the ground connection into condition to be closed by the downward movement of the switch-hook. so that the calling subscriber upon hanging up his receiver energizes the release mechanism of the -connector and ell'ects the release or disconnection between the lines.

It will be obvious that in this system the .resistances of the magnets may be varied to any extent Vconsistent with the successful lili isst/,sce am,

operation of the same. Not only may the re sistances of the line relays (for er ple the line relays 124 and 125 ci the selec". r D) be varied, but the resistances of the operating magnets (for example the release magnets 45, 129 and 139) `may likewise be Vvaried. l It is also obvious that the springs used as contacts may be adjusted in` any manner desired and their tensions varied to any extent in order to control the speed and ope-ration of the armatures associated with them. For example, the -springs el the motor magnet relay 79 may be stillcned or weakened, as may be found convenient or desirable.

Attention is called to the coils 4l of the line switch C. As shown, the windings of each of these coils should never be superimposedthat is, the windings on each coil should be separated as shown, and in a manner more particularly illustrated in the.

motor magnet relay 79. In regard to this motor magnet relay it should be stated, and i t is perfectly obvious, that` althoughA it is shown as a double-wound differential coil. the upperwinding is not absolutely neces sary, since the system will operate without it.

lVhat I claim as my intention is l. In .a telephone system, a called' subscribers line, a switch individual thereto 'for trunking therefrom, provided with a controlling magnet Vconnected in the line circuit, means for feeding talking current through the said magnet to the called line, said magnet having windings constituting the sole resistance for regulating the iow of talking current to the line, a calling line, manually-operated calling mechanism therefor, and means for, extending connection from the calling line to the called line, said means .including an automatic switch individual to the calling line and responsive to and simultaneously with the manual operation of said calling` mechanism.

:2. In a telephone system, a plurality of l:ines,.automatic means for trucking a call ing line into connection with a called line,

comprising individual trunking switches for the said l1nesa connector for finding the called 1ine,a callingjmechanism for each line, said connector responsive to va varying number of impulses in accordance with the difieient digits of the called number, means including a trunk line for feeding talking current to the calling line, alltallring current for the called line being fed directly through elements of the individual switch thereof.

3.` In a telephone system, a called line, a connector for sjeizin said line, said connector provided with a relay ad'apted'to remain energized during conversation, means by which the calling 'subscriber deenergizes said relay to signal the called subfor extending' connection :trom a calling line I to a called line, a common battery normally connected to the called line, means by which the called line receives talking current onlyI through the medium of its normal connection with said battery, and means for opening' said normal connection when the called line becomes a callingr line. y

In a telephone system, subscribers lines, individual trunking switches ior said lines, each switch provided with a dil'llcrcntiallvwmind trip magnet normally bridged across its-allotted telephone line, a release able plunger-arm controlled by each trip magnet and provided with means for opening the bridge thereof/when the subscriber calls, means for supplyingtalking current through the trip magnet of a called line, the diilerential windingsot` said trip-map;- nets proventineactuation'v of the'called subscribers individual switch "during conversation, a ringer relay for controlling the iow of ringing vcurrent to the called subscribe1"s line, and means for delincrgizing said ringer relay to signal ythe called subscriber.

6. In a telephone system, a. lcalling subscribers line, a called subscriber-s line, an automatic connector common to said lines, means fcrfsupplying talking current to the lines, said connector' included in the path of talking current to the calling line, but eX- cluded from the path of talking current to the called line, and a calling' mechanism for' controlling said connector, which latter is operated by a varying number-of impulses in accordance with the different 'digits of the called number. l

7. In a telephone system, automatic means for trunkinf:I a calling line into connection with a called line, including anv automatic connector controlled by the ,calling subscriber, means for supplying talking current to the lines, said connector included in the path of talking current to the calling line, A-

but excluded from the path of talking current to the called line, and a calling mechanism for controlling vsaid connector, which latter is operated by a varying number of impulses in accordance with the differentv digits of the called number.

8. In a telephone system, a called line, means common to twoor more subscribers for seizing said line, an automatic switch responsive when the Said line is used as a oallingline, but adapted to remain normal 'when the line is called, means for supplying current through elements o it' said switch to the called line for 'talking purposes, a ring ing relay adapted to be energized during connection with a called line, and means for denergizing said relay igor applying ringing current to said line.

9. In a telephone system, a called line, an automatic connector' common to two or more subscribers for seizing said line responsive to the call, an automatic switch responsive. when the said line is used as a calling line7 but adapted to remainnormal when the line is called, means for supplying current through elements of said automatic switch to the called line for talking purposes, a ringing relay adapted to be energized during connection with a called line, and means for d energizing saidrelay for applying ringing current to 'said line.

10. In a telephone system, a. called line7 an individual trunlring switch therefor responsive only when the line is used asa calling line, means for seizing said line responsive to a call, means i'or supplying current through elements of said individual switch to the called line for talking purposes, a ringing relay adapted to be energized during insane@ connection With a called line, and means for denergizing said relay for applying ringing current to said line. l

il. In a telephone system, a called line, ai non-numerical trunking switch individual to said line7 responsive only when the line calls7 means for seizing said line responsive f calling lines, and means whereby the called' lines receive talking current only through connections which are individual thereto from a`\com'mon battery.

Signed by me at Chica o, Cook county, Illinois, this 26th day of une, 1907.

Winsen L; CAMPBELL.

Witnesses:

EDWARD D. FALns. ARTHUR B. SPERRY. 

